In a synchronized wireless communications system, a common method for a remote mobile unit to request access to the system is to send an uplink access message to a fixed base station. An example of this uplink access message is a random access channel (RACH) message found in a time division multiple access (TDMA) type Global System for Mobile Communications (GSM) system. Each time a base station detects a RACH message, physical and logical resources are allocated for the remote mobile unit to communicate. The physical and logical resources in a typical system are limited, resulting in degradation of system performance and preventing other potential mobile units from accessing the system whenever a RACH message is falsely detected. The development of reliable procedures to minimize false RACH message has a very high priority in the system. These procedures should be designed to have a negligible adverse impact on the detection sensitivity of actual RACH messages.
In a conventional GSM system, there are built in protections to maximize signal detection that do not address the problem of false detection. For example, information bits in a RACH message are encoded with cyclical redundancy code (CRC) parity check bits that allow for noise corrupted RACH messages to be detected and discarded by the base station. However, this CRC parity check may still allow false RACH messages to be detected. Since the base station is detecting the presence of RACH messages many times a second, other criteria that characterizes the quality of the received signal need to be developed to avoid overwhelming the resources of the base station with false RACH message detections. Therefore, it is desirable to provide a technique that reduces or avoids the detection of false access messages in order prevent unnecessary allocation of system resources.